The present invention relates to the detection of ionizing radiation, particularly to a method and apparatus for detecting ionizing radiation and moving sources, and more particularly to a method and apparatus for detecting high levels of ionizing radiation emitted from vehicles moving at high speeds along public roadways.
The problem of detecting moving objects that emit ionizing radiation has become significant. Scrap metal moving into scrap yards and steel mills must not contain significant radioactive contamination. The result of a truckload, or railcar load of scrap metal with radioactive contamination moving into a scrap yard could be the decontamination of the yard at great cost. The result of a contaminated load of scrap metal moving into a steel mill could be the decontamination of the mill. High decontamination costs have been encountered in such situations. The scrap metal, with the hidden radioactive contamination, may be moving into the yard or mill by truck, by railcar or by conveyor belt.
Prior art for monitoring ionizing radiation contamination in the loads of trucks and train cars for such purposes is well known, such as in U.S. Pat. Nos. 5,705,818 and 5,679,956. However, in this prior art, the preference is that the vehicle not move more than five or six miles per hour, as higher speeds decrease the sensitivity of the detection system. Thus, these systems are inherently impractical for monitoring vehicles when on public roads or railways or objects on a conveyor moving at moderate or full speed. It is therefore highly desirable to provide a new and improved radiation monitoring system.
Another prior art system can detect ionizing radiation in vehicles moving nearly 19 miles per hour by using an adaptive filter method. Such method uses at least three separate detectors, and data from a reading off of a vehicle from each detector is compared to a reading of background radiation, and only if all three detectors detect sufficiently high levels of radiation is an alarm sounded. In this way, false alarms are minimized. However, such a system is limited as it still is not practical for vehicles moving at highway speeds or on interstates moving at interstate speeds. Additionally, such a system may be susceptible to false negative readings in the event one of the detectors should have detected a sufficiently high level of radiation to trip an alarm but did not, causing the system to fail to sound an alarm.
The need for monitoring high levels of ionizing radiation from vehicles traveling at speeds in excess of 19 miles an hour as well as at lower speeds is clear in the wake of the Sep. 11, 2001 terrorist attacks in New York City and the increasing threat around the world from terrorist groups. Terrorists, such as World Trade Center attack suspect Osama bin Laden, claim to have nuclear and chemical weapons, according to accounts published in Pakistani newspapers and other Middle East news sources. U.S. officials have stated that terrorists are trying to acquire nuclear materials and weapons. Thus, there is the possibility that a terrorist could surround a car bomb with dangerous radioactive material. Under those circumstances, it is necessary to explore the question of whether or not authorities can detect vehicles carrying radioactive sources.
Vehicles cannot be regularly stopped and inspected with a handheld detection device because interstate highway traffic would be snarled, the program would require a large number of inspectors and police to back them up, and a terrorist could avoid the obvious roadblock by using an alternate route. An effective system must be inexpensive, detect radioactive material in a vehicle, identify the vehicle so that it can be stopped by police, avoid slowing down traffic to a crawl, and be so inconspicuous that a terrorist will not notice it and circumvent the system by using a secondary road. Therefore, it is highly desirable to provide a new and improved radiation monitoring system capable of regularly taking accurate readings above 19 miles per hour and from vehicles moving at a wide range of speeds including top speeds on highways, interstates and thoroughfares. It is also highly desirable to provide a new and improved radiation monitoring system that can provide visual identification of a vehicle corresponding to the detector reading therefrom. It is further highly desirable to provide a new and improved radiation monitoring system that is inconspicuous at least until such time as detection and identification may be made.
Prior art systems employ different means and methods for taking into account and compensating for background radiation levels as well as the natural shielding effect of most vehicles as they pass through the scanning area of the radiation detector. However, to take advantage of such means and methods requires additional skill and know-how for computing the specific relationships of timed readings and generating algorithms and other formulas and methods for arriving at accurate measurement results. Furthermore, each such means or method has an impact on the sensitivity of the system that may be used. Therefore, it is highly desirable to provide a new and improved radiation monitoring system that uses a simple yet unique method for arriving at accurate radiation detection results despite sensitivity considerations caused by readings generated from naturally occurring radioactive material and other background radiation sources. It is also highly desirable to provide a new and improved radiation monitoring system that uses the background readings detected in a way that affirmatively differentiates high level readings from materials carried by a vehicle traveling at high speed. It is further highly desirable to provide a new and improved radiation monitoring system that can monitor radiation with a high degree of sensitivity without concern of anomalous background radiation sources.
Finally, it is highly desirable to provide a new and improved radiation monitoring system having all of the above identified features.
It is therefore an object of the invention to provide a new and improved radiation monitoring system.
It is also an object of the invention to provide a new and improved radiation monitoring system capable of regularly taking accurate readings above 19 miles per hour and from vehicles moving at a wide range of speeds including top speeds on highways, interstates and thoroughfares.
It is an object of the invention to provide a new and improved radiation monitoring system that can provide visual identification of a vehicle corresponding to the detector reading therefrom.
It is also an object of the invention to provide a new and improved radiation monitoring system that is inconspicuous at least until such time as detection and identification may be made.
It is an object of the invention to provide a new and improved radiation monitoring system that uses a simple yet unique method for arriving at accurate radiation detection results despite sensitivity considerations caused by readings generated from naturally occurring radioactive material and other background radiation sources.
It is also an object of the invention to provide a new and improved radiation monitoring system that uses the background readings detected in a way that affirmatively differentiates high level readings from materials carried by a vehicle traveling at high speed.
It is an object of the invention to provide a new and improved radiation monitoring system that can monitor radiation with a high degree of sensitivity without concern of anomalous background radiation sources.
Finally, it is an object of the invention to provide a new and improved radiation monitoring system having all of the above identified features.
In the broader aspects of the invention there is provided a radiation monitoring system for detecting levels of radiation emitted from moving objects traveling at a wide range of speeds, including the high speeds normally encountered with vehicles traveling on highways, interstates, thoroughfares, railroads and conveyors. At least two and preferably three or more ionizing radiation detectors are employed, spaced apart in series along the direction of travel of the moving object or vehicle. The object or vehicle is monitored for radioactivity and the results are transmitted and processed at a central location. The individual results from each detector for a particular object or vehicle are summed and averaged over the number of detectors used clearly distinguishing the fluctuating background radiation detected at each detector from the consistent high levels of radiation detected from those moving objects or vehicles measured and are cooperatively linked by an identification system such as a web cam or other photographic device which obtains visual identification of the objects and vehicles emitting the abnormally high levels of radiation detected.